Bosoite, a new silica clathrate mineral from Chiba Prefecture, Japan. (20th December 2020)

• Record Type: Journal Article
• Authors: Momma, Koichi; Ikeda, Takuji; Nagase, Toshiro; Kuribayashi, Takahiro; Honma, Chibune; Nishikubo, Katsumi; Takahashi, Naoki; Takada, Masayuki; Matsushita, Yoshitaka; Miyawaki, Ritsuro; Matsubara, Satoshi
• Is Part Of: Mineralogical magazine. Volume 84:Number 6(2020)
• Page Start: 941
• Page End: 948
• Publication Date: 2020-12-20
• Subjects: bosoite, -- new mineral, -- silica clathrate, -- chibaite, -- hydrocarbon, -- Japan; Mineralogy -- Periodicals; Mineralogy -- Great Britain -- Periodicals; 549.05
• DOI: 10.1180/mgm.2020.91
• Languages: English
• ISSNs: 0026-461X

Abstract

Abstract: Bosoite (IMA2014-023) is a new silica clathrate mineral containing hydrocarbon molecules in its crystal structure. Bosoite can be considered structurally as a silica analogue of the structure-H gas hydrate, where guest molecules are trapped in cage-like voids constructed of the host framework. The mineral occurs in the Miocene tuffaceous sedimentary rocks at Arakawa, Minami-boso City, Chiba Prefecture, Japan. Bosoite is hexagonal, and it crystallises as an epitaxial intergrowth on chibaite crystals, with the {0001} of bosoite parallel to octahedral {111} form of chibaite. Crystals are colourless and transparent with vitreous lustre. The calculated density is 2.04 g/cm 3 . The empirical formula (based on 2 O apfu and guest molecules assumed as CH4 ) is Na0.01 (Si0.98 Al0.02 )Σ1.00 O2 ⋅0.50CH4 ; the end-member formula is SiO2 ⋅ n C x H2 x +2 . Bosoite has the space group P 6/ mmm, with the unit-cell parameters a = 13.9020(3) Å, c = 11.2802(2) Å, V = 1887.99(6) Å 3 and Z = 34. The crystal structure of bosoite was refined by single-crystal X-ray diffraction and converged to R 1 = 4.26% for the average model and R 1 = 2.96% for the model where all oxygen sites are split.